The ATTLIST declaration defines an attribute on a previous defined ELEMENT definition within a DTD.

Declaration Types

#REQUIRED

<!ATTLIST ElementName AttributeName AttributeType #REQUIRED>

Defines a required attribute AttributeName on the element ElementName. The attribute must exist, and value of the attribute must comply with the type rules for AttributeType.

#IMPLIED

<!ATTLIST ElementName AttributeName AttributeType #IMPLED>

Defines an optional attribute AttributeName on the element ElementName. The attribute does not have to exist, but if it does the value of the attribute must comply with the type rules for AttributeType.

#FIXED

<!ATTLIST ElementName AttributeName AttributeType #FIXED AttributeValue>

Defines an attribute AttributeName on the element ElementName. The value of the attribute can only be the value specified in AttributeValue, and must comply with the type rules for AttributeType. If the attribute not present in the containing element, then as the XML Parser reads the document it will automatically add it,  giving it the value specified in AttributeValue.

AttributeType

The type of an attribute can be either 'CDATA', 'ID', 'IDREF', 'IDREFS', 'ENTITY', 'ENTITIES', 'NMTOKEN', 'NMTOKENS'. Each of these types has its own rules describing the ranges of values that they are allowed to contain.

The AttributeType can also be an enumeration, that is to say it can contain one of a number of pre defined values. There are 2 forms of enumerations.

• A list of values that must comply with the type rules for 'NMTOKEN'.
• A NOTATION attribute, in with case the values that must match the name of NOTATION's declared elsewhere within the DTD, this NOTATION data is an instruction to the processing application, and not strictly speaking considered part of the XML Data. An element can only have 1 NOTATION attribute.

AttributeValue

A quoted string containing the fixed value that the attribute must take. The standard rules for escaping attribute values apply (i.e. '&', '<' and '"' must be escaped if a double quote is used around the value, and '&', '<' and ''' must be escaped if a single quote is used around the value.

Examples

<!ATTLIST test myAttr CDATA #IMPLIED>

<test myAttr="some value"/>

<test/>

<!ATTLIST test myAttr CDATA #REQUIRED>

<test myAttr="some value"/>

<test/>

<!ATTLIST test version CDATA #FIXED '1.2'>

<test version="1.2"/>

<test/>

<test version="5.7"/>

<!ATTLIST test userID ID #REQUIRED>

<test userID="123456"/>

<test userID="Joe Bloggs"/>

<!ATTLIST test fruit (apple | pear | bannan) #REQUIRED>

<test fruit="pear"/>

<test userID="pineapple"/>

<!NOTATION js PUBLIC "JavaScript 1.0">
<!NOTATION cs PUBLIC "CSharp 2.0">
<!NOTATION js PUBLIC "Perl 4.0">

<!ATTLIST test 
    scriptEngine NOTATION (js|cs|perl) #REQUIRED>

<test scriptEngine="cs"/>

EBNF Syntax

The following EBNF describes the form the declaration takes.

[52]   AttlistDecl         ::=       '<!ATTLIST' S Name AttDef* S? '>'
[53]   AttDef              ::=       S Name S AttType S DefaultDecl
[54]   AttType             ::=       StringType | TokenizedType | EnumeratedType
[55]   StringType          ::=       'CDATA'
[56]   TokenizedType       ::=       'ID' | 'IDREF' | 'IDREFS' | 'ENTITY' | 'ENTITIES' | 'NMTOKEN' | 'NMTOKENS'
[57]   EnumeratedType      ::=       NotationType | Enumeration
[58]   NotationType        ::=       'NOTATION' S '(' S? Name (S? '|' S? Name)* S? ')'     [VC: Notation Attributes]
[59]   Enumeration         ::=       '(' S? Nmtoken (S? '|' S? Nmtoken)* S? ')'    [VC: Enumeration]
[60]   DefaultDecl         ::=       '#REQUIRED' | '#IMPLIED' | (('#FIXED' S)? AttValue)